This invention relates to tubes and is particularly concerned with apparatus for, and a method of, shaping an end of a tube as may be required to facilitate the joining of that tube end to the surface of another body. More particularly the invention was developed to facilitate the shaping of a tube end for joining that end to a further body by welding and as such is primarily concerned with metal or plastics tubes.
It is conventional practice when welding an end of a tube to a non-flat surface, which may conveniently be regarded as the convex surface of a second tube, to profile the end of the tube, for example to provide an arcuate or saddle shape, so that that end can be positioned adjacent to or mounted to sit on the surface in substantially complementary relationship. If the tube has negligible wall thickness then by appropriate profiling its end may be regarded as making face-to-face contact with the curved surface of the second tube. However, if the tube has a substantial wall thickness, such as heavy duty tubes as are used, for example, in the construction of a framework or jacket in the assembly of off-shore drilling rigs (where it is not unusual for the tube to have a length in the order of 4 meters, an external diameter of 180 cms and a wall thickness of 12 cms) then, depending upon the positioning of the end of the tube on the curved surface and/or the angular relationship between the two tubes a condition may be obtained on the profiled end of the tube whereby, at one position the edge of the tube profiled end face on the inside surface of the tube will contact the curved surface while at a second position (peripherally spaced from the first position) the edge of the tube profiled end face on the outside surface of the tube will contact the curved surface. This particular configuration may result in an effective line of contact between the profiled end face of the tube and the curved surface which line progresses at least in part radially across the wall thickness of the tube end face between its inner surface and its outer surface. With thick walled tubes such as those aforementioned it has hitherto proposed to provide a continuous bevel or chamfer around the radially outermost peripheral edge of profiled end face so removing the corner portion of the tube between its outer peripheral surface and the end face and thereby reducing the thickness of the wall around the end of the tube. By so chamfering or bevelling the tube wall an effective peripheral channel may be formed when the tube is mated with the curved surface to which it is to be welded within which channel weld filler material may be applied to secure the bodies together. While such form of preparation of the tube end may be regarded as acceptable in conditions where the surface of the tube subtends an angle with the curved surface or tangent to that curved surface which is greater than, say, 55.degree. it is found that if the aforementioned subtended angle is less than 55.degree. the portion of the channel and adjacent part length of the tube in the region of the minimum subtended acute angle becomes extremely deep with the result that a considerable amount of welding time and filler material may be required to fill the channel and form an efficient weld. In an attempt to alleviate this difficulty of inefficient usage of weld material it has been proposed to provide so called transition bevelling whereby bevel portions are cut manually at discrete regions along the periphery of the profiled end face of the tube so that such bevel portions are located primarily at positions required to facilitate welding of the tube end to the further body and it is an object of the present invention to provide apparatus and a method which may facilitate such shaping and bevelling of the tube end.